Query on MAX on date column, and COUNT of another column

Question

I performed the following query with cte's, but I was wondering if there was a simpler way of writing the code, maybe with subqueries? I'm retrieving everything from one table SALES, but I'm using 3 columns: AgentID, SaleDate, and OrderID.

WITH RECENT_SALE AS(
    SELECT AGENTID,(
    SALEDATE,
 ROW_NUMBER() OVER (PARTITION BY AGENTID ORDER BY SALEDATE DESC) AS RN
 FROM SALES
)
,
 COUNT_SALE AS (
    SELECT AGENTID,
 COUNT(ORDERID) AS COUNTORDERS
 FROM SALES
)

  SELECT RECENT_SALE.MRN, 
 SALEDATE, 
 COUNTORDERS

 FROM RECENT_SALE
 INNER JOIN COUNT_SALE ON RECENT_SALE.AGENTID = COUNT_SALE.AGENTID;

Answer 1

Try this:

 SELECT 
    saledate,
    AGENTID, 
    count(orderid) over(partition by AGENTID order by saledate)
 FROM SALES
 group by  
    saledate,
    AGENTID

Answer 2

It looks to me like you're just trying to get the total number of sales per agent as well as the date of his or her most recent sale? If I understand your structure correctly (and I may not), then it seems pretty straightforward. I'm guessing orderid is the primary key of SALES ?

SELECT agentid, MAX(saledate) AS saledate -- Most recent sale date
     , COUNT(orderid) AS countsales -- total sales
  FROM sales
 GROUP BY agentid;

There does not seem to be any need for CTEs or subqueries here.